1. Field of the Invention
The present invention relates to an active roll control system vehicle for a vehicle. More particularly, the present invention relates to an active roll control system (ARCS) which can actively control roll of a stabilizer bar connected to a pair of upper arms mounted respectively at both sides of a vehicle body through stabilizer links.
2. Description of Related Art
Generally, a suspension system of a vehicle connects an axle to a vehicle body so as to control vibration or impact transmitted from a road to the axle not to be directly transmitted to the vehicle body when driving. Accordingly, the suspension system of a vehicle prevents the vehicle body and freight from being damaged and improves ride comfort.
Such a suspension system includes a chassis spring relieving impact from the road, a shock absorber reducing free vibration of the chassis spring and improving the ride comfort, and a stabilizer bar suppressing roll of a vehicle (it means that a vehicle inclines with reference to a length direction of the vehicle body).
Herein, the stabilizer bar includes a straight portion and both ends.
Both sides of the straight portion are mounted at the vehicle body, and the both ends are mounted at a lower arm or a strut bar that is a suspension arm through the stabilizer link.
Therefore, in a case that left and right wheels move to the same direction (upward direction or downward direction), the stabilizer bar does not work. On the contrary, in a case that the left and right wheels move to the opposite direction (one moves upwardly and the other moves downwardly), the stabilizer bar is twisted and suppresses the roll of the vehicle body by torsional restoring force.
That is, when the vehicle body inclines toward a turning axis by the centrifugal force in a case of turning or heights of the left and right wheels is different from each other by bump or rebound of the vehicle, the stabilizer bar is twisted and stabilizes position of the vehicle body by torsional restoring force.
Since a conventional stabilizer bar, however, has a constant torsional rigidity, it is insufficient to secure turning stability under various driving conditions by means of torsional elastic force of the stabilizer bar only.
Recently, an active roll control system having an actuator including a hydraulic pressure cylinder and connected to an end of the stabilizer bar so as to control roll actively has been developed.
The active roll control system uses the hydraulic pressure cylinder instead of the stabilizer link connecting the lower arm and the end of the stabilizer bar so as to change a connecting length between the end of the stabilizer bar and the lower arm. Therefore, total roll stiffness of a vehicle due to the stabilizer bar is increased.
FIG. 1 is a partial perspective view of a conventional suspension system for a vehicle, and FIG. 2 is a schematic diagram of a suspension system for a vehicle to which an active roll control system for the vehicle according to conventional arts is applied.
Referring to FIG. 1, an active roll control system according to a conventional art may actively increase total roll stiffness of a vehicle due to the stabilizer bar 1 so as to enhance anti-roll characteristic actively.
Referring to FIG. 1, the active roll control system includes a stabilizer bar 1, a stabilizer link 3, a sliding unit 5 disposed on a lower arm 7 that is a suspension, and a driving unit 6.
Herein, the stabilizer bar 1 includes a straight portion and both ends. And both sides of the straight portion are mounted at a bracket 13 on a sub frame 11 of the vehicle body through a mounting bushing 15.
An upper end of the stabilizer link 3 is connected to an end of the stabilizer bar 1 through a ball joint BJ.
The sliding unit 5 is connected to a side of the lower arm 7 through a housing 21 and rail plates 23 are disposed within the housing 21. A connector 25 connected to a lower end of the stabilizer link 3 is movably disposed to the plate 23. If the driving unit 6 is operated, the connector 25 moves along a vehicle width direction.
The driving unit 6 includes a motor 27 and a lead screw 39 as a rotary shaft of the motor 27.
The housing 21 is opened upward, shaped as a box shape, and connected to the side of the lower arm 7.
A protruded portion 33 is formed to an end of the housing 21 and is connected to a lower portion of a knuckle 17 through a ball joint BJ.
The rail plates 23 are disposed within the housing 21 along vehicle width direction.
The lead screw 39 is disposed along the rail plates 23 through the housing 21.
The connector 25 is disposed between the rail plates 23 within the housing 21 and engaged with the lead screw 39.
The connector 25 is connected with the lower end of the stabilizer link 3 through a ball joint BJ.
The cover 29 to which a slot is formed thereto corresponding to operation distance is connected to the opened upper portion of the housing 21.
The active roll control system may drive the motor 27 according to driving conditions so as to change a connecting position of the stabilizer link 3 on the lower arm 7.
Due to variation of the connecting position of the stabilizer link 3, a total roll stiffness of a vehicle due to the stabilizer bar 1 is increased.
However, referring to FIG. 2, an active roll control system according to a conventional art is offset from a plane connecting points P1, P2 and P3, where connecting portions of the lower arm 7.
In a case of turning or heights of the left and right wheels is different from each other by bump or rebound of the vehicle, compliance effect may occur due to the offset.
The motor 27 of the driving unit 6 operates the stabilizer link 3 away from moving area where the lower arm 7 may move so that the motor 27 is needed to output high power. If the lower arm 7 bumps or rebounds, the lower arm 7 moves the stabilizer link 3 along vehicle width direction during bumping or rebounding, so that high load may be applied to the motor 27.
Particularly, while the point P1 is positioned near a wheel center, however the driving unit 6 is operated away from the point P1, and thus characteristic of lateral force may be deteriorated.
Also, since the motor 27 is positioned where vibration and fly rocks may induce chipping, and thus durability of the motor may be deteriorated.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.